［Swift］不使用storyboard创建视图

1. 工程配置时不指定Main interface。
   或者删除info.list的key：Main storyboard file base name

2. appdelegate中设置根视图控制器。

@UIApplicationMainclass AppDelegate2 :UIResponder, UIApplicationDelegate{    var window : UIWindow?    func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject : AnyObject]?) -> Bool{        self.window = UIWindow(frame: UIScreen.mainScreen().bounds)        self.window!.backgroundColor = UIColor.redColor()        self.window!.makeKeyAndVisible()        let controller: UIViewController? = UIViewController()        self.window!.rootViewController = controller        return true    }}